The goal of this proposal is to assess U.S. hospital capacity for bioterrorism and public health emergency response using advanced computer modeling techniques. This work will advance the scientific understanding of health system responses to medical crises, and create decision making tools that will help hospital and public health planners improve response strategies for both intentional (i.e., bioterrorism-related) and natural outbreaks of human disease (i.e., epidemics). Ultimately this research will permit more evidence-based policy analysis and decision-making regarding resource allocation for public health preparedness and hospital surge capacity. Capacity assessment will be accomplished by developing discrete event simulation models of hospital treatment for the six Category A bioterrorist agents and for Severe Acute Respiratory Syndrome. These models will balance hospital bed capacity in each of the 313 U.S. Hospital Referral Regions against simulated epidemic curves that reflect both disease and public health response variables (e.g., outbreak type and size, effectiveness of initial mass prophylaxis response). By estimating regional capacity for outbreaks of these biological agents, this study will offer a new picture of national public health preparedness. A second component of this project will evaluate patterns of emergency health service utilization in the setting of public health emergencies. Patient "surges" at eight New York City emergency departments will be evaluated during the 2001 anthrax attacks using administrative data from the New York Presbyterian Healthcare System. This study will complement the national-level hospital capacity assessment by evaluating neighborhood-by-neighborhood variability in patient arrivals, since the response of the public to such disasters has important implications for mass prophylaxis planning. Taken together, these studies will advance the science of public health preparedness and provide tools to improve forecasting of health system capacity and for planning an efficient epidemic response.